This invention relates to apparatus for manually pouring molten metal into a mold during a metal casting process and, in particular, to an improved tiltable ladle which permits pouring of molten metal under operator control whereby metal spillage, heat loss from the molten metal during transfer to the mold and required operator concentration may be minimized.
In the manual metal casting industry, castings are poured from manually controlled pouring ladles which have been filled with molten metal at a molten metal source and transported by crane or by a monorail system to the molding area where the metal is poured from the ladles into the individual molds. These conventional pouring ladles are cylindrical in shape about either a vertical or horizontal axis, but in some instances are segmental in shape about a horizontal axis, and are fitted with a pouring lip or spout. In normal foundry practice today, these ladles are rotated about a horizontal axis to permit metal to overflow the pouring lip and spill from the ladle in a direction perpendicular to the axis of rotation or tilt of the ladle and directly into a pouring cup on the mold surface. Furthermore, although not in general practice today, it is known that molten metal also may be poured into runner boxes for directing the molten metal to a pouring cup on the mold surface instead of pouring directly into the pouring cup. Such previously known pouring ladles are shown, for example, in U.S. Pat. No. 284,005 to Hainsworth; U.S. Pat. No. 4,025,060 to Fujie; and U.S. Pat. No. 4,112,998 to Sato.
The requirements for pouring a satisfactory mold can be quite rigid, depending upon the design of the casting to be poured. In general, these requirements are as follows:
1. The metal must have sufficient temperature to flow properly within the mold cavity.
2. Metal flow must be commenced and maintained at a sufficiently rapid rate of flow to maintain a level of metal within the pouring cup throughout the pour, preventing inpurities floating on the metal surface being carried into the mold cavity.
3. Metal flow must be maintained continuously throughout the pour.
4. Metal pressure within the mold must be held to a level that will prevent damage to the mold interior.
In addition to the above, the economics of production require that pouring be terminated before metal has overfilled the pouring cup and run out over the mold surface and solidified.
With a conventional pouring device, where pouring is directed perpendicular to the axis of rotation of the ladle such as shown in U.S. Pat. No. 4,112,998 to Sato, the physical configurations of the mold and the pouring device usually prevent the pouring lip of the device from being brought into close proximity with the pouring cup. Thus, the molten metal trajectory to the pouring cup must be directed accurately to fulfill the requirements of a satisfactory pour. If the pouring cup position changes from mold to mold, the molten metal trajectory must be changed requiring high operator skill and concentration to avoid excessive spilling and damage to the casting. Furthermore, with front lip pouring ladles, substantial heat loss of the molten metal occurs when the molten metal stream passes through the air in a trajectory between the pouring ladle and the pouring cup. This heat loss increases with the length of this trajectory.
It should therefore be apparent that proper pouring from front lip pouring ladles directly into a pouring cup or into a transfer trough requires a high degree of operator coordination and extreme concentration. When it is also considered that the operator is working in a very hot and dirty environment and that any slight miscalculation of metal trajectory or flow will result in the probable splashing and loss of molten metal or the destruction of a casting, it is obvious that a great need exists for a device to optimize operator performance and minimize required operator skills.
There are other conventional pouring devices generally used in a continuous iron pouring line which have ladles which pour in direction coincident with the axis of rotation of the ladle during pouring. Such ladles are shown in U.S. Pat. Nos. 3,940,021; 3,997,461 and 4,044,927. In all of these devices, the ladles are provided with nozzles to pour directly into the pouring cup in a mold. The iron pouring lines are automatic and the molten metal is always poured to the same location. This apparatus cannot be used when the pour cup changes from mold to mold such as in a manual or custom foundry.